Systematic Error

Problem: 20-30% qualified crystal resonators before delivery was recognized as unqualified by customers during their acceptance check.

Analysis: It is caused by systematic error of measuring equipment between customer and supplier. At present, the precision of measuring equipment of quartz crystal resonator can reach 2×10-6 when resonators do not carry load capacitance, but the precision is hard to guarantee when crystal component with load capacitance. Manufacturers promise the precision of frequency haulage is 1 PF capacitance. Actually, instruments are not accurate when used to examine tiny capacitor, the precision of the instrument can reach 0.2-0.5 PF, and in consequence, the error of 5 -10 PPM is easy to occur, especially fundamental crystal resonator with small load capacity. Each PF capacitance can produce about 50×10-6 haulage. Furthermore, testing equipment of different factory and the same instrument with different testing method will engender different results.

The solution to the problem: To quartz crystal resonator whose frequency deviation is strictly required (e.g. less than 10PPM), it is advisable that clients provide the sample or manufacturers offer the sample. After confirming systematic errors of direction and figure by both parties, suppliers shall revise before delivery.